The Monumental stadium in Cuscatlan, about 25 miles northeast of capital San Salvador, was hosting a quarter-final clash between domestic clubs Alianza and FAS. However, the venue's capacity of 44,836 is understood to have been exceeded after hopeful spectators forced their way through an access gate.

The resulting flood of fans saw play suspended just 16 minutes into the match as chaos unfolded on-field. Horrific images from the match showed bodies strewn in tunnels and gangways as medics saw to those injured in the crush.

"It was an avalanche of fans who overran the gate," commented Pedro Hernandez, president of El Salvadoran football's first division. "Some were still under the metal in the tunnel. Others managed to make it to the stands and then to the field and were smothered."

Footage of the incident in Cuscatlan showed the moment fans recognise the seriousness of the crush as it unfolded. Some supporters could be seen fighting to free others from beyond the metal barriers inside a tunnel.

Mauricio Arriaza, director of the National Civil Police, said nine fans died at the hospital, with three more deaths confirmed from different hospitals. "Salvadoran soccer is in mourning," he added.

Reports suggested officials were concerned about fake tickets to the match being sold, with an investigation into the matter already believed to be underway.